How safe is your tap water? Check for the bio-films formed on your house tap, which can be potentially hosting bacteria and you will get the answer. A study conducted on drinking water sources in 46 villages of Bangalore North taluk has revealed a higher biocide activity in the water, resulting in bio-film formation in the pipes. One third of the water samples collected were considered highly polluted, exceeding the ISI, WHO and USPH standards. The study was conducted by Dr N Nandini, Department of Environmental Science, Bangalore University. "Bio-film development on surface is a result of several physical, chemical and microbial processes resulting in bio-corrosion and bio-fouling process. The process of corrosion of water distribution system (pipes) can be prevented if bio-film formation is arrested,' according to Dr Nandini. Bacteria "The biocide activity against microbial suspension in pure culture may have little significance as a lower concentration of biocide is needed to kill the planktonic micro-organisms in water. But a much higher level is required to be controlled, which will form bio-films. Two common bacteria are tested for their ability to colonise galvanised iron pipe (GI) and Polyvinyl chloride (PVC) surfaces, survive various biocide treatments,' she said. "Bio-films are an an important survival mechanism for many extra-cellular parasites. The development of bacterial population as bio-films within the water distribution system in northern part of Bangalore has led to long-term bacteriological problems. We have something called minimum inhibitory concentration (MIC) test, which allows certain level of biocide in water. The disadvantages of this traditional system needs a thorough check,' she said. However, the experiment and the solution to the problem is still at the laboratory level. Dr Nandini said even the solution they are prescribing will be applicable to small areas and can't implemented in very large networks. "This was the experiment our department conducted and it had a limited purpose. If organisations like BWSSB is interested, we can work with them too. We can explore possibility of coming up with a solution which can be implemented in a bigger way,' she added.